An ECG monitor is an instrument for providing a real-time or delayed display and/or a printed record of a patient's ECG waveform. The ECG monitor is interconnected with the patient by means of a set of electrodes and associated conductors commonly referred to as a patient cable. The ECG waveform is typically displayed by means of a cathode ray tube (CRT), and the printed record is typically provided by means of a strip-chart recorder or its equivalent. An ECG monitor is a diagnostic instrument, i.e., it assists the operator in evaluating the physiological condition, and in particular the cardiac condition, of the patient.
A defibrillator is a therapeutic instrument particularly useful in conjunction with an ECG monitor to assist in curing certain cardiac irregularities, particularly ventricular and atrial fibrillation. The defibrillator is typically interconnected with the patient via a set of large paddle electrodes and associated conductors, and operates to apply a high energy DC pulse to the patient via the paddle electrodes when appropriately triggered by an operator.
In one type of prior physiological instrument, an ECG monitor and a defibrillator are combined and electrically connected within a single housing. In such an instrument, circuitry is generally provided to allow the ECG monitor to be connected to the patient through the paddle electrodes that are normally associated with the defibrillator. Physiological instruments are also known in which the ECG monitor and defibrillator are modular components that are capable of operating either independently, or in an interconnected manner in which the defibrillator is mechanically and electrically connected to the ECG monitor.
The mechanical connection between the modular components of an ECG monitor/defibrillator instrument, i.e., between the ECG monitor and the defibrillator, is an important feature of such an instrument. For example during routine use in a hospital, the instrument is usually operated with the ECG and defibrillator modules connected. However, emergency situations can arise in which it is necessary to rapidly transport the defibrillator to another part of the hospital, or to a location outside the hospital. The mechanical connection between the defibrillator and the ECG monitor must therefore permit rapid separation of the units, in spite of the fact that the units may be comparatively heavy. However, the mechanical connection must also be rigid when separation is not desired, and must permit the combined instrument to be picked up by lifting only one of the components, without risk of separation.